for a yeared at administration kept the most damaging information the fatalities in mexico, a secret. with univision's help we were able to something we knew, the serial numbers of guns to something we didn't a crime in mexico. to put a face on one of america's most embarrassing political scandals. a home covered in blood after gang members kill, 16, many teenagers at a birthday party in juarez mexico. many use in the massacre traced to "fast and furious". >> they are waiting for an answer. they want to know what happened and why they didn't stop these guns from leaving the united states and ending up in this, in these crimes. >> reporter: spanish language network univision and fox news obtained a list of 100,000 weapons recovered in mexico and compared of the serial numbers with the 2,000 guns sold in "fast and furious." nearly two dozen matched, connectings untold number of injuries and fatalities to the u.s. program. this woman lost two sons to "fast and furious" guns. >> they feel helpless. they don't know what to do. we interview one of them and they say, who is going to pay for